Creating functional engineered variants of the single-module non-ribosomal peptide synthetase IndC by T domain exchange.

Non-ribosomal peptide synthetases (NRPSs) are enzymes that catalyze ribosome-independent production of small peptides, most of which are bioactive. NRPSs act as peptide assembly lines where individual, often interconnected modules each incorporate a specific amino acid into the nascent chain. The modules themselves consist of several domains that function in the activation, modification and condensation of the substrate. NRPSs are evidently modular, yet experimental proof of the ability to engineer desired permutations of domains and modules is still sought. Here, we use a synthetic-biology approach to create a small library of engineered NRPSs, in which the domain responsible for carrying the activated amino acid (T domain) is exchanged with natural or synthetic T domains. As a model system, we employ the single-module NRPS IndC from Photorhabdus luminescens that produces the blue pigment indigoidine. As chassis we use Escherichia coli. We demonstrate that heterologous T domain exchange is possible, even for T domains derived from different organisms. Interestingly, substitution of the native T domain with a synthetic one enhanced indigoidine production. Moreover, we show that selection of appropriate inter-domain linker regions is critical for functionality. Taken together, our results extend the engineering avenues for NRPSs, as they point out the possibility of combining domain sequences coming from different pathways, organisms or from conservation criteria. Moreover, our data suggest that NRPSs can be rationally engineered to control the level of production of the corresponding peptides. This could have important implications for industrial and medical applications.

[Max Mohr (1891 - 1937) - a physician in search of independence]. / Max Mohr (1891-1937)--ein Arzt auf der Suche nach Unabhängigkeit.

Max Mohr (1891-1937) was a physician and one of the most successful writers during the period of the Weimar Republic (1919-1933). The biography of Max Mohr is of particular importance for the understanding of his works. Since--aside from the literary producing--his medical occupations were constitutive in his life, this article focuses on the physician Max Mohr. The pursuit of personal independence was a central theme in his life. Though working in a private practice would have enabled him to lead a civic life in Munich, Mohr--newly-married in 1920--decided to move into Wolfsgrub near Rottach at Tegernsee. Mohr increasingly applied himself to his literary producing and frequently visited Berlin. In 1934, Mohr was forced to emigrate to Shanghai because of his Jewish heritage. There he quickly succeeded in building up his own practice, thus securing an economic existence. Mohr died on November 13th, 1937.